This invention relates to flame retardant polyamide compositions. More particularly, this invention relates to flame retardant polyamide compositions which have excellent anti-drip characteristics when exposed to flames.
The trend toward integration of electronic components has led to an increasing need for plastic materials having much greater heat resistance and flame retardant properties, particularly for use in connectors, circuit boards, semiconductor packages and the like. Where such devices are used continuously, or are used in demanding environments, they may encounter extremely high temperatures. Further improvements in heat resistance and flame retardant properties for such materials are thus continually being sought by the industry.
Partially aromatic polyamides, typified by polymers comprising hexamethylene diamine terephthalamide units, have excellent mechanical strength, rigidity, heat resistance and moisture resistance. These polyamides are finding wide acceptance for use as engineering plastics, particularly in applications where elevated temperatures and severe environments may be encountered, for example, in electrical appliance parts, in connectors and similar parts for electrical and electronic devices and in a variety of automotive applications. Filled compositions comprising such polyamides in combination with reinforcing fillers such as glass fibers are also useful where further improvement in heat resistance and rigidity is required.
Like most other thermoplastic resins, polyamides are subject to burning. When the polyamide is to be used in applications requiring self-extinguishing characteristics and flame retardant properties it is necessary to resort to the addition of a fire retardant. Halogen-containing organic compounds such as a halogenated polystyrene, polydibromostyrene, or a condensation product of brominated phenol to polyamides have been used to impart fire-retarding properties in certain polyamide fomulations. Antimony compounds are also used in combination with the halogen-containing organic compounds to improve flame retarding properties.
In addition to flame retarding for some polyamide applications, it is required that the polyamide composition, when exposed to a flame, have a reduced tendency to drip. A dripping polymer is a hazard and technology has been developed to reduce the dripping by adding a PTFE additive. However, PTFE when used in a polyamide formulation can agglomerate and cause problems in the molding process used to make molded parts from the polyamide composition. The art, therefore, needs a polyamide composition that is flame retardant, has good anti-drip properties and does not agglomerate. This invention provides for such polyamide composition.